All they need to do is put transparent block on city areas so people can't jump and climb up in cities... not hard to do and pretty basic stuff in 'most' games. Just like old school 2D RPG they tell the map sections which part of the map is walkable (land) and which ones are not walkable (water) same thing applies for 3D just like how FFXIV's cliff works, like limsa for example right now there is transparent wall so you can't drop off on the areas without any rails (hope you can jump off later though...)